For many years, gear coupled, counter-rotating vibratory drive assemblies have been provided as vibratory drive assemblies for generating linear vibratory motion to convey and separate particulate material, and for other applications in which linear vibratory motion is beneficial.
Although various types of counter-rotating vibratory drive assemblies have been suggested, the standard counter-rotating vibratory drive assembly uses a gear-coupled arrangement to provide synchronous motion of two unbalanced drive shafts that are driven by a single motor. The present day commercial units are an outgrowth of the design illustrated in U.S. Pat. No. 1,999,213 granted to Shaler on Apr. 30, 1935. Somewhat similar designs are illustrated in the early U.S. Pat. Nos. 1,517,587 granted to Roth and 1,827,586 granted to Keefer.
Although such gear coupled, counter-rotating vibratory drive assemblies have been commercially popular, they have not been without significant maintenance and reliability problems. Such problems have been highlighted in more recent patents such as U.S. Pat. Nos. 3,473,396 (Schwake et al.); 4,212,731 (Wallin et al.); and 4,255,254 (Faust et al.).
The Schwake et al. U.S. Pat. No. 3,473,396 mentions the severe shocks that are encountered by the gears upon startup and shutdown. The Schwake et al. design is intended to eliminate such severe shocks by the use of frictional wheels rather than gears.
Others have suggested that instead of using a single motor for driving both shafts through a gear coupling, that it is advisable to utilize two separate motors through separate drives that can be synchronized. Examples of such techniques are illustrated in the Wallin, et al., U.S. Pat. No. 4,212,731. It, too, criticizes the gear coupled arrangement as requiring unnecessary mass and increased maintenance costs. Furthermore, it mentions that experience has shown that gearing is undesirable since tremendous forces are developed in the gears. The Faust, el al. U.S. Pat. No. 4,255,254 emphasizes that the gear coupled, counter-rotating systems require unnecessary bulk of the gears that interconnect the two unbalanced shafts providing increased costs and also generating expensive maintenance and generating substantial frictional heat that must be dissipated.
The Roder et al. U.S. Pat. No. 3,053,379 granted Sept. 11, 1962 is concerned with a material-handling vibrating system utilizing counter-rotating unbalanced shafts. In FIG. 6c of the patent, there is illustrated a drive system for a spiral conveyor having two vibrating drives. Each of the drives has a gear coupling with outboard eccentrics mounted on the shafts. Although the eccentrics are offset from each other, there is no suggestion or illustration that the eccentrics have radii greater than the radii of the matching gears that interconnect the two shafts.
One of the principal objects of the present invention is to provide a very simplified gear coupled, counter-rotating vibratory drive of the gear coupled type that dramatically reduces maintenance, increases reliability, and furthermore decreases noise. Although the previous prior art has not spcifically dealt with the noise problem, it is very significant and should be dramatically diminished.
These and other objects and advantages of this invention will become apparent upon reading the following detailed description of the preferred embodiment.